1. Field of the Invention
The present invention relates to a rotary disc valve with a stationary valve plate provided with a vacuum connection, a rotary slide member mounted so as to be movable between first and second valve positions, wherein the slide member has a breakthrough connecting the vacuum connection to a suction opening in the first valve position, wherein the suction opening is connected to an aerating opening in the second valve position, and wherein both valve positions determine a suctioning angle.
2. Description of the Related Art
Rotary disc valves of the above-described type are used particularly for controlling the vacuum of suction devices which are arranged at opening drums of a feeder. Such opening drums can be used for opening envelopes and folded sheets which are closed at the heads thereof without overlay folds and for placing the envelopes or folded sheets onto a collector chain. The rotary disc valve is arranged at one end of the shaft of the opening drums provided with the suction devices and is connected through a flexible line to a vacuum pump or another suitable vacuum source. The suction devices are connected to the vacuum source during each rotation of the opening drums. The flaps of the sheets to be opened are suctioned and, when the opening drums rotate further, the envelopes or folded sheets are opened in the middle thereof. Subsequently, the suction devices are once again aerated and the spread-apart envelopes or folded sheets are placed onto the collector chain. It is essential that the suctioning and aerating moments are adapted precisely to the envelopes or folded sheets and particularly to the sizes thereof.
In a rotary disc valve which is known in the art, the suction devices can be adjusted at the circumference of the opening drum in order to adapt to different products. In addition, it is possible to adjust the valve plate on which the flexible valve line is arranged. When the valve plate is adjusted, the moment of suctioning as well as the moment of aerating are simultaneously shifted. Consequently, when adjusting the opening drum, it was necessary in the past to adjust the suction devices at the circumference of the opening drum, on the one hand, and to adjust the control disc, on the other hand. Therefore, the optimum adjustment was relatively cumbersome in the past and had to be carried out while the drum is standing still.
JP 050 92 679 A discloses a rotary disc valve of the above-described type in which a valve plate 22 is provided which is rotatable in order to adjust the suctioning moment. For this purpose, a clamping ring 24 is provided which can be releasably connected to the valve plate by means of a locking screw 25. This clamping ring must be released for adjusting the valve plate. The rotary disc valve is mounted at the end of a hollow shaft of the opening drum. For adjusting the opening moment, it is required that the opening drum stands still. Consequently, an adjustment during operation is not possible.
Therefore, it is the primary object of the present invention to provide a rotary disc valve of the above-described type which is particularly suitable for an opening drum of a feeder and which makes possible a simpler adjustment of the moments when suctioning begins and ends.
In accordance with the present invention, the above-described object is met by providing means for adjusting the size of the suctioning angle.
Contrary to the present invention, in rotary disc valves of the prior art the suctioning angle was always fixed and could not be adjusted. Consequently, when the moment of aerating was adjusted, the suctioning moment was always adjusted simultaneously and inevitably by the same angle. In the rotary disc valve according to the present invention, on the other hand, the aerating moment can be adjusted while the moment of suctioning remains fixed and, thus, the size of the suctioning angle can be adjusted within a predetermined range. By adjusting the aerating moment, the suctioning angle becomes smaller or greater.
In accordance with a preferred feature, the rotary disc valve includes a slide member which is adjustable and particularly rotatable during operation for changing the size of the suctioning angle.
The rotary disc valve according to the present invention can be realized with a relatively small number of robust components.
In accordance with a preferred embodiment, the rotary disc valve is composed of a valve plate on which the flexible vacuum line is mounted, a slide member and a control disc as the means for adjusting the size of the suctioning angle. The slide member is fixedly secured to a shaft and rotates together with the shaft. The stationary control disc is mounted at the outer end of the shaft and includes an axial passage connected through a breakthrough of the slide member to a suction duct. This suction duct preferably extends through the shaft of the opening drums.
In accordance with another embodiment of the invention, the valve plate has a recess extending in the circumferential direction, wherein a slide member is mounted in the recess so as to divide the recess into two chambers. One of the chambers is connected through a passage to the vacuum source and the other chamber is connected through a passage to the aerating opening. This embodiment also requires essentially only three simple and robust components.
The rotary disc valve is preferably used in a suction drum, particularly the opening drum of a feeder, especially for a saddle stitcher.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.